Prediction of surfactant dysfunction in term infants by the click test

Pulmonary surfactant dysfunction (inactivation, deficiency) has been implicated in term neonates with respiratory failure. This study has evaluated the click test, a biophysical test for surfactant function, which will be useful in rapidly and reliably identifying term neonates with surfactant dysfunction. Samples of tracheal and or gastric aspirates (0.2 ml) from 55 neonates, varying from 36 to 42 weeks of gestational age, with respiratory distress and fractional inspired oxygen concentration requirements of > 0.5 were shaken with 95% ethanol. Once bubbles formed the samples were examined in air-free water under a microscope. In a positive click test, the bubbles rhythmically increase and then decrease in size, denoting the presence of active surfactant. When few bubbles were observed, the specimen was labelled as equivocal, and if none were seen, it was called negative. Surfactant dysfunction (negative or equivocal test) was consistently seen in respiratory distress syndrome (RDS), transient tachypnea of the newborn, and severe meconium aspiration syndrome (MAS). Preliminary data suggest that the click test will provide a rapid and early diagnosis of surfactant dysfunction in term neonates. This should facilitate early treatment with exogenous surfactant in RDS, by early diagnosis of surfactant deficiency, and provide justification for immediate and ongoing surfactant treatment in newborns with MAS. The click test can provide a diagnostic tool for surfactant dysfunction and deficiency in randomized controlled trials of therapy in those disease states in which exogenous surfactant therapy may be useful.